You should probably take your foot off the gas if you see a white bicycle sitting alone, without a rider outside your window.
The white bicycles are known as "ghost bikes," and they represent a tragedy that happened along the road.
How Did Ghost Bikes Start?
According to GhostBikes.org
, the first somber memorials involving white bikes popped up in St. Louis in 2003.
The Ghost Bike is placed near the crash site where a bicyclist was killed or hit on the street. The bike is typically locked to a street sign and accompanied with a sign that explains the significance of the memorial.